Search

Therapeutic drug monitoring (TDM) of elexacaftor, tezacaftor, ivacaftor (ETI) could be a useful tool to increase efficacy and decrease the risk of adverse effects in people with Cystic Fibrosis (pwCF). It is however unclear whether drug exposure should be monitored by assessment of trough (C min ) levels or determination of the area under the curve (AUC). Hence, in this study the correlation between measured C min concentration and AUC was evaluated. Serial plasma samples, including C min , were drawn after administration of ETI in order to calculate the AUC and assess the correlation between the two parameters. A linear correlation between C min and AUC 0-24h was found, with Pearson's r correlation coefficients of 0.963, 0.908 and 0.860 for elexacaftor, tezacaftor and ivacaftor, respectively. Exposure of ETI may be monitored by assessment of C min levels., Competing Interests: Declaration of competing interest The authors have no conflict of interest to declare., (Copyright © 2024. Published by Elsevier B.V.)

Purpose: Cystic fibrosis (CF) is a monogenetic disease caused by mutations in the gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR) protein and affecting multiple organs, including the lungs and liver. Almost 90% of people affected carry at least 1 Phe508del CFTR mutation. Medical treatment with the CFTR-modulating drug elexacaftor-tezacaftor-ivacaftor (ETI) has been proven to be efficacious in carriers of at least 1 Phe508del CFTR mutation. Use of ETI in patients with CF (pwCF) and liver cirrhosis is still controversial. Therefore, stepwise introduction of ETI in pwCF and liver cirrhosis Child-Pugh A or B was evaluated using clinical and therapeutic drug monitoring., Methods: Seven consecutive pwCF received ETI. Four dosing steps were defined, at each of which the patients underwent clinical examination, routine blood tests, and therapeutic drug monitoring. Exposure of elexacaftor, tezacaftor, and ivacaftor was assessed by means of determination of AUC., Findings: ETI was successfully introduced and maintained in all pwCF. In those with Child-Pugh B cirrhosis (n = 2), diminishment of the dose as recommended by the label resulted in AUC values that were lower than the mean AUC values in pwCF without hepatic impairment, as reported previously., Implications: Despite the limitations of this small case series, stepwise elevation of ETI dose did not induce clinical adverse effects or increases in serum liver test results under strict clinical follow-up and therapeutic drug monitoring, and may allow tolerable introduction of this therapy in pwCF and cirrhosis Child-Pugh A and possibly B., Competing Interests: Declaration of Competing Interest None., (Copyright © 2023 The Author(s). Published by Elsevier Inc. All rights reserved.)

Background: The novel cystic fibrosis transmembrane conductance regulator (CFTR) modulators, ivacaftor, lumacaftor, and tezacaftor, are the first drugs directly targeting the underlying pathophysiological mechanism in cystic fibrosis (CF); however, independent studies describing their pharmacokinetics are lacking. The aim of this study was to develop a quantification method for ivacaftor and its 2 main metabolites, lumacaftor and tezacaftor, in plasma and sputum using liquid chromatography with tandem mass spectrometry., Methods: The developed method used a small sample volume (20 µL) and simple pretreatment method; protein precipitation solution and internal standard were added in one step to each sample. Liquid chromatography with tandem mass spectrometry was performed for a total run time of 6 minutes. The method was validated by assessing selectivity, carryover, linearity, accuracy and precision, dilution, matrix effects, and stability., Results: The selectivity was good as no interference from matrices was observed. In the concentration range from 0.01 to 10.0 mg/L, calibration curves were linear with a correlation coefficient >0.9997 for all compounds. The within-run and between-run accuracy were between 99.7% and 116% at the lower limit of quantitation (LLOQ) and between 95.8% and 112.9% for all concentrations above LLOQ for all analytes in plasma and sputum. Within-run and between-run precisions were <12.7% for LLOQ and <6.7% for the higher limit of quantitation. Samples were stable, with no significant degradation at examined temperatures and time points. Clinical applicability was revealed by analyzing samples from 2 patients with CF., Conclusions: The presented method enables simultaneous quantification of ivacaftor, lumacaftor, and tezacaftor in plasma and sputum and is an improvement over previous methods because it uses smaller sample volumes, a simple pretreatment protocol, and includes tezacaftor. In future studies, it can be applied for examining pharmacokinetics characteristics of new CF transmembrane conductance regulator modulators., Competing Interests: The authors declare no conflict of interest., (Copyright © 2021 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the International Association of Therapeutic Drug Monitoring and Clinical Toxicology.)